This invention relates generally to the field of compressors for use in air conditioning systems, such as automotive air conditioning systems. In particular, this invention relates to a new design for an automotive air conditioning system that utilizes a hybrid mechanically and electrically driven compressor, which has improved efficiency.
Some designs for air conditioner or refrigeration units for cars, trucks, trains, ships and airplanes permit the units to be powered by an engine when the engine is operative, and by a battery driven motor when the engine is off. To make vehicles more energy efficient, an integrated starter generator (ISG) can shut the engine off when the vehicle is stopped to minimize emissions and improve fuel economy. An electric motor can drive the compressor of the air conditioning system when the engine stops.
An increasing number of hybrid vehicles are being manufactured with a view towards increased fuel efficiency and reduced emissions. One type of hybrid vehicle has an electric motor that generates driving force in combination with an internal combustion engine that typically utilizes fossil fuel. The electric motor can assist in driving the hybrid vehicle. The motor can be powered by batteries that can be charged when the engine is running or by an external charger.
It is desired to use smaller displacement engines in hybrid vehicles, and to also reduce the power demands placed on the engines by accessories, such as power steering pumps and air conditioning compressors.
In many automotive systems, an internal combustion engine is operatively connected to an air conditioner compressor via a belt and pulley mechanism. It is also known in the art for an air conditioner compressor to be provided with an electric motor to drive the compressor when the engine is not running. The drive shaft of the compressor is extended out through the casing and can be operatively connected to the pulley via a one-way clutch, which is engaged when the pulley is driven. The pulley is locked to the compressor shaft when the clutch is engaged so that the engine drives the shaft, but the pulley will idle in relation to the compressor shaft when the engine is not driving the pulley and the compressor shaft is turned by the electric motor.
If continued air conditioning or refrigeration is required while the engine is stopped, the electric motor drives the compressor. When the engine is restarted, the electric motor is stopped, and the clutch engaged again to drive the compressor.
Further information on air conditioning systems and hybrid mechanically/electrically driven compressors can be found in the patent literature, articles, and books, such as but not limited to U.S. Pat. No. 2,246,244, U.S. Pat. No. 2,902,205, U.S. Pat. No. 3,211,365, U.S. Pat. No. 4,179,248, U.S. Pat. No. 4,411,141, U.S. Pat. No. 4,738,584, U.S. Pat. No. 5,178,520, U.S. Pat. No. 5,722,257, and U.S. Pat. No. 5,934,089, all of which are incorporated by reference as if reproduced in full herein.
In a fixed displacement hybrid compressor system, frequent cycling between engine drive and motor drive, as well as the increased inertial requirements from the motor, lead to increased wear on the clutch of the hybrid system versus that of a system that is engine driven only. Since in a fixed displacement compressor the same compressor displacement is present regardless of whether the engine or electric motor is driving the compressor, power use inefficiencies arise. Power use efficiencies may also arise in hybrid variable displacement compressors. Thus, it is desired to have a more efficient hybrid air conditioning system and to better match compressor displacement and air conditioning system capacity to requirements.
In an embodiment, a hybrid compressor is formed of a main compressor driven by an engine-operated pulley and an auxiliary compressor driven by an electric motor. Preferably, the two compressors share a common housing and system connections, such as suction and discharge chambers and manifolds. In a preferred embodiment, the compressors are operable independently of each other, permitting one or both compressors to be activated. If one compressor has a smaller fixed displacement than the other, three levels of displacement and power requirements are achieved, wherein the first compressor may be driven and the second compressor idle, the first compressor may be idle and the second compressor driven, or the compressors may be simultaneously driven. In an alternative embodiment, one or both of the compressors may be a variable displacement compressor, wherein higher efficiencies may be obtained in matching cooling requirements to capacity and displacement for each of the compressors and engine or electric motor operating parameters.
The compressors are generally positive displacement types that use a displacement mechanism, such as a scroll, reciprocating piston, or rotating vane.
In a preferred embodiment, a common housing is provided in which is located both a low displacement compressor scroll that is drivable by a high speed, high efficiency electric motor and a larger displacement compressor scroll that is drivable by an engine.
In an embodiment, a hybrid stacked scroll compressor is provided with a controller for selectively activating (starting) or deactivating (stopping) the engine and/or engaging or disengaging a clutch operatively connecting the engine to a compressor drive shaft. The controller also selectively activates or deactivates the electric motor. Either or both the engine and the electric motor driven compressors are activated in response to the demand for cooling or air conditioning, while accommodating battery and engine operating parameters.
The present invention also includes a method of operating an electric motor driven compressor and an engine driven compressor in response to the demand for cooling or air conditioning, and battery and engine operating parameters.
It is to be understood that both the preceding summary and the detailed description that follows are intended merely to be exemplary and to further explain the invention claimed. The invention may be better understood by reference to the following detailed description read in conjunction with the accompanying drawings.